Film sprocket clamp



June 27, 1950 H. N. FAlRBANKs FILM sPRocKET CLAMP Filed March 9, 1946 FIG. 2.

' FIG INVENTOR HENRY N. FAlRBA NKS ATTORNEYS Patented June 27, 1950 UNITED STAT PATENT OFFICE FILM SPROCKET CLAMP Henry N. Fairbanks,Beverly-'II-ills, Galif, assigner 'to vMitchell Camera Corporation, West Hollywood; Calif., Ia.cmporationfof Delaware ApplicationlMarcns, 1946;ser`ia1'No. 653,408

(C11 l 22H-2.3)

k1'1y Claims; 1;

This invention has to do with an'improve'd lm handling sprocket for use iny metio-n picture equipment and the like. The `primary objects of the invention are to facilitate threading 'the nlm between the sprocket and the guide rollers by simplifying the manual operations which are reiquired; and to reduce the 'space necessary for the 'entire sprocket assembly by greatly reducing the relative motion of the parts when the lil-m is to -be releasedfrom or admitted tor-engagement with the sprocket. An important characteristic fof-a fllm 'sprocket designed `according to my invention in its :preferred form is that when thers'procket is in-the open-or nlm releasing position the'fmain body of 'the lsprocket itself :and the entire .structure of the film clamping'rollers retain their nor;- 'ma'l operating positions. Only the 'sprocket head and the associated sprocket disk which 'carries the film engaging teeth need be moved, and even the motion of these parts is relatively slight.

`A full understanding of these and other featuresof my invention will be made clear by description of a preferred and illustrative embodiment, for which reference is made to the accompany-ing drawings Fig. 1 is a partially 'cut away end viewfof the sprocket assembly in its normal operatingposition;

Fig. 2 is a longitudinal section on line 2-2 of Fig. 1, showing the parts in their normal operating `r.positions Fig. 3v is a similar sectionvshowing the sprocket iniits film releasing or open position;

Fig. 4 is a transverse section on line 44-of Fig. 5 isy a transverse section on line 5-5 of Fig.'3; and

Fig. 6 is a'longitudinal section, similar-to Fig, 3, but showing a modificationv of thek design 'by which the sprocket may be temporarily locked` in its 'open position.

In the `figures the sprocket shaft is shown at ID, and is journalled in the bearing Il whichlis mounted in a rigid part of the frame l2 ofthe machine illustrated as a flat plate. Thesprocket itself comprises the body which is rigidly mounted on shaft l0, and sprocket 'disk 2| and sprocket head `22 which are connected to 'bodyl 20 by' means to be described. The lm guiding o'r `confining means may be of any suitable form; That rmeans is here illustrated as rollers 30 which rotate freely on their shafts 3|, rigidly attached tori-'ame l2 by-the threaded portions shown at 32, andere retained upon their shafts by 'screws i33i These rollers '30 -carr-y nlm engaging'surfacesil,

43 andV 45 which cooperate respectively wi'tiifth'e surface 42 on `sprocket head 22, and surfaces 44 and 46 on sprocket body 2B to restrain the nini-F in a 'radaldir'ection and to insure engagement of the `sprocket'teeth 23 with perforations 24-of'th'e' film; To avoid injury tothe Vcentral-lyl located picture area of the film the surface of 'the vrollers is relieved 'at 41 and the sprocket-1mb -isrelieved at y48. The rollers are similarly relieved at vES/and the sprocket hub at5ll to yavoid ycontact with'the sound ytrackv area `of the nlm-near its'inner edge. The sprocket teeth 23; which project through apertures 424 in the film, are accommodated Aby the groove 5| located between surfaces f4| andi43 of guide rollers 30. The lateral position of vfilm'l is normally determined-"by its engagement `with the sprocket teeth; in absence lci such engagement it is restricted by -the Iinner flange 54pm sprocket body 20 and by outer flange 55 fon sprocket head 22.

To permit insertion or removal of the nlm ac'-i cording to my invention, the jtoothed. sprocket disk 2| and the sprocket head 22 are connected to sprocket body Zofinsuch a way that they are coaxial with sprocket shaft I Il during normaloperation but may ybe vmoved transversely of the axis into such a 'position that sprocket teeth L23'1no 1longer vengage the film perforations and that-outter flange 55 `no longer restricts theOutWardla-t- 'eral displacement ofthe nlm. Under these con: dition's, asisclear 'from' Fig. 3, Ithe -iilm may be freely' withdrawn from or inserted between-the sprocketk body and the guide rollers. The dis' tance throug-hwhich the head and-sprocket ydisk drop 'is sufficient not only lto move the uppermost sprocket tooth below the peripheryof-surface 4'4 of the sprocket body, butalso to move theftwo adjacent sprocketteeth `down `far enough toat leastnot project beyond that surface and prefer ably tobe slightly radially inside of it.v With the sprocket-teeth in that position, Vand with head flange 55 havinga diameter at least `equal to 'thfe maximum vtooth diameter, the film yisprevented from -contacting the sprocket 'teeth during inser tion and removal.

Y-In the preferred embodiment illustrated, sprocket head 2-2 and disk' 2| are Yconnected to sprocket body20 by means of ystuds 60.- These are rigidly mounted in theholes '16| in `thefinner -face of sprocket head 22by screws '62. 'Thelflanges'tSl on ystuds i seat against the inner face lofthe sprocket head and" are' accommodated k'by -he Ihele-s 66 in sprocket disk-12|. Sprocket Ihub "2'05is recessed 'at -1'0 fand lthe-disk "l1-"l is pressed-tightly into Athe recess,-1eavirrg- -a space "lZfbtweentl lisgslsimgmf L inner surface of the disk and the bottom surface 13 of recess 10. Studs 60 extend through the holes 14 in disk 1|, which are considerably larger than the diameter of studs 60 and are so placed as to be coaxial with the studs when the parts of the sprocket assembly Iare in their normal coaxial operating relation. The heads 68 of studs 60 are of oblong shape, as shown in Fig. 5, their long-er dimension being oriented tangentially, and they slidingly engage the inner surface of disk 1|, thus retaining head 22 and disk 2| in sliding contact with the outer face of sprocket body 20. Due to the relatively small diameter of stud heads 68 in a radial direction, they are free to move within the recess 'l2 in a plane at right` angles to the sprocket axis as freely as is permitted by the clearance between studs 60 #and holes 'I4 in disk 1|.

The transverse sliding motion of sprocket disky 2| and head 22 relative to sprocket body 2n is controlled by plunger 81]. The main body 8| of this plunger is cylindrical Vand ts slidingly in the axial hole 82 in sprocket body 29 and in the coaxial hole 83 in disk 1|. Plunger 8| is urged outwardly in hole 82 by the coil spring 85. In normal operating position its outward motion is limited by contact of its shoulder 90 with the inner falce of sprocket disk 2|. Outward of shoulder 90 is a cylindrical portion 9| which fits accurately in the central holes 93 in sprocket head 22 and disk 2|. The outer portion'95 of plunger 80 is of relatively small diameter, and extends well outside sprocket head 22. T'le two cylindrical sections 9| and 95 of plunger 89 are joined by the generally conical section 92.

When the sprocket is in normal operation, plunger 80 assumes its extreme outward position, shown in Fig. 2, its cylindrical section 9| restraining the transverse sliding motion of sprocket disk 2| and head 22, so that these parts are in effect rigidly joined to sprocket body 20. The plunger centers the several parts co-axially, and the studs connect the parts to rotate together. If now plunger 80 is pressed in to the position shown in Fig. 3, compressing spring 85, the sliding motion of sprocket disk 2| and head 22 is no longer restrained, and they drop by gravity into the position shown in Figs. 3 and 4. In practice this motion is limited either by contact of the Wall of hole 93 with the cylindrical section v95V of the plunger, or by contact of studs |50 with the walls of holes 114 in disk 1|, or in both ways, depending upon the dimensions of the parts. If that displacement is limited by the studs, and not limited by the pin in such manner that the displacements of both head and disk are equal; then the stud flanges can, by fitting the disk holes loosely, allow a greater displacement of the disk than of the head. With the sprocket in v'this dropped position the film can readily be inserted or withdrawn, as pointed out above. Upon release of plunger 8|) it is again forced outward by spring 85, the conical section 92 of the plunger acting as a Wedge and lifting the sprocket disk 2| and head 22 back into their operating positions (Fig. 2), where they are effectively locked as before, by cylindrical portion 9| of the plunger.v In the drawings this cylindrical portion is shown to be long enough to project through sprocket disc 2| and engage hole 93 in sprocket head 22.l Thusit effectively defines the axes of both these members, making it unnecessary for the flanges l(iii on studs 6U to fit accurately holes -66 `in the sprocket disk. On the other hand, if anges 65 do t holes,- ,66 closely, this prevents relative transverse asiaoml f imotion of sprocket disk 2| and head 22, and it becomes sufcient for cylindrical section 9| of the plunger to engage only sprocket disk 2|. In general, the sprocket disk and the head may be regarded as if they were integral. Except that it is desirable to make the head and sprocket diskof dierent materials, the head may be nothing more than an annular integral extension of the disk to provide the annular surface 42 and the protective shoulder 55 for the edge oi the nlm.

`The generally conical portion 92 of plunger 8|) may be shaped in Various ways. In Fig. 6 is shown a modification in which this conical surfaceV terminates at its outer end in a slight shoulder 96. This has the elect, after the plunger has been pressed in and the sprocket disk and head have dropped to their open position as shown in the ligure, of preventing the plunger from moving outward. The sprocket is thus temporarily locked in its open position, facilitating the operation of threading. A slight upward pressure on sprocket head 22 is then suicient to disengage shoulder 96 from the inner corner of sprocket disk 2|, and the sprocket is then returned automatically to its operating position, as described before. Or a slight rotation of the sprocket, either lby hand or by starting the mech7 anism in operation, will cause the sprocket and head to move to or toward their centralized position, allowing the plunger to move out to lock them in that position. When, in rotation, the relatively protruding part of head surface d2 approaches a roller flange 4|, the flange presses inwardly on the nlm and thus on the head to move it and the sprocket toward centralized posi-v tion. And this same initial rotation may also engage the sprocket teeth in the film perforations if they have not previously been so engaged.

A comparison of Figs. 1 and 4 or of Figs. Zand 3 will show the very slight motion which is necessary to change the sprocket yassembly from its operating position to its open position. This permits other apparatus to be placed in the imme diate neighborhood of the sprocket without inter,- fering with its operation. The length of the sprocket body, as shown in the drawings, is greater than is necessary. In fact it will be Iapparent from the drawings that the entire extension of sprocket body 2l? inward of flange 54 can readily be eliminated, guide rollers Blbeing altered accordingly, and the inner edgeoi the lm thus brought as close to the face of frame/I2 as operating requirements permit. v As has been indicated, the preferred form of the invention is one in which the shiftable part of the sprocket 4(essentially the sprocket disk 2|) is relatively small-that is, in the for-m of a relatively thin disk. However, the invention is applicable .to a thicker disk and even to one vwhich may be so thickl as to provide or include the major portion of what is here described as the body 20 of the sprocket. v'llhis can be readily visualized from Fig. 2 simply by assuming that sprocket disk 2| be increased in thickness by an extended `-cylindric portion to the right of the sprocket teeth, the sprocket body 20 being commensurately shortened axially,y and studs 60 being Aincreased in length so as to laccommodate the thickened sprocket disk. In such an instance the body. 2 9 becomes mainly or solely (just as it is primarily in the preferred design) a amount or Carneyfor the'shiftable member vwhich carries the sprocket teeth. The term body as used in the following .claims is t0 be understood in Such Sense-4 1. In lm drive devices which include a sprocket unit mounted for rotation about its axis, and la film confining element mounted to overlie a portion of the periphery of the sprocket unit and to confine a film against the sprocket unit; a sprocket unit comprising a body, a circular toothed sprocket member, means mounting the sprocket member on the body to be movable between a position concentric with the body and a position eccentric therewith, and releasable means separate from the mounting means for holding the sprocket member in its concentric position.

2. In lm drive devices which include a sprocket unit mounted 'for rotation yabout its axis, and a lm Iconfining lelement mounted to overlie a portion of the periphery of the sprocket unit and to confine a nlm against the sprocket unit; a sprocket unit comprising a body of gener-al cylindric form having an end face which is perpendicular to the body axis, a sprocket disk, means for confining the disk against the end face of the body and allowing sliding movement of the disk between a position concentric with the body and a position eccentric therewith, and releasable means separate from the confining means for holding the sprocket disk in its concentric position.

3, A sprocket unit comprising a body of general cylindric form mounted for rotation about its axis, a circular toothed sprocket member, means mounting the sprocket member on the body to be movable between a position concentric with the body and a position eccentric therewith, and releasable means separate from the mounting means for [holding the sprocket member in its concentric position.

4. A sprocket unit comprising a body of general cylindric form mounted for rotation about its axis and having lan end face normal to its axis, a sprocketdisk, means for conning the disk against the end face of the body and -allowing sliding movement of the disk between positions concentric and eccentric with the body, and releasable means separate from the confining means for holding the disk in its concentric position.

5. A sprocket unit as dened in claim 4 and in which the disk confining means comprises a circular head lying Iagainst the outer face of the disk, and studs which connect both the head and the disk to the body.

6. A sprocket unit as defined in claim 4 and in which the disk confining means comprises a circular head lying against the outer face of the disk, and studs which connect both the head and the disk to the body, the studs being rigidly lattached to the head, passing through the vdis-k and connected to the body to have play therein in a direction parallel to the plane of the disk.

7. A sprocket unit as dened in claim 4, rand in which the disk centering means comprises an axial-ly movable pin mounted Iaxially in the body and having an outer part of relatively small diameter projecting outwardly through an axial bore in the sprocket disk, the pin having an intermediate outwardly tapering, formation of general conical form adapted to enter the central bore in the sprocket disk by outward movement of the pin, and a spring tending to move the pin outwardly.

8. A sprocket unit 'as dened in claim 4, Vand in which the disk centering means comprises an axially movable pin mounted axially in the body and having an outer part of relatively small diameter projecting outwardly through an axial bore in the sprocket disk, the pin having an intermediate outwardly tapering, formation of general conical form adapted to enter the central bore in the sprocket disk by outward movement of the pin, a cylindric formation at the base of the conical formation adapted to nt the central bore in the sprocket disk land a shoulder at the inner end of the oylindric formation adapted to bear outwardly against the inner face of the disk, and a spring tending to move the pin outwardly.

9. A sprocket unit las dened in claim 4, and in which the disk centering means comprises `an axially movable pin mounted axially in the body and having an outer part of relatively small diameter projecting outwardly through an axial bore in the sprocket disk, the pin having Aan intermediate outwardly tapering, formation of general conical form adapted to ent-er the central bore in the sprocket disk by outward movement of the pin, an annular'shoulder formation at the outer end of the conical formation yadapted t0 catch on the inner face of the disk at the edge formed by the central bore therein, and` a spring tending to move the pin outwardly.

10. In iilm drive devices which include a sprocket unit mounted for rotation about its axis, 'and a film c'onning element mounted to overlie va portion of the periphery of the sprocket unit and to conne a lm 'against the sprocket unit; a sprocket unit comprising a body, a circular toothed sprocket member, means mounting the sprocket member on the body to be movable between a position concentric with the body and a position eccentric therewith, the sprocket member having a Icentral axial opening therethrough, and means for releasably holding the sprocket member in its concentric position comprising a tapered plunger mounted to slide -centrally and axially of the sprocket body and through the opening in the sprocket member, said tapered plunger in one of its axial positions tting said opening snugly.

11. In lm drive devices which include a sprocket unit mounted i'or rotation about its axis, and a lm confining element mounted to overlie a portion of the periphery of the sprocket unit and to conne a lm against the sprocket unit; a sprocket Lmit comprising a body of general lcylindric form having an end face which is perpendicular to the body axis, a sprocket disk, means for confining the disk against the end face of the body and allowing movement of the disk between a position concentric with the body and a, position eccentric therewith, the sprocket member having a central axial opening therethrough, and means for releasably holding the sprocket disk in its concentric position comprising a tapered plunger mounted to slide centrally and axially of the sprocket body and through the opening in the sprocket disk, said tapered plunger in one of its axial positions tting said opening snugly.

HENRY N. FAIRBANKS.

REFERENCES CITED The following references are of recordA in the flle of this patent:

UNITED STATES PATENTS' Number Name l Date 927,942 Buswell et al July 13, 1909 1,348,183 Rayeld Aug. 3, 1920 

